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- Karczewska-Lindinger, Magdalena, et al.
(författare)
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Force Generation Profiles of Para-Nordic Sit-Skiers Representing Different Physical Impairments
- 2021
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Ingår i: Journal of Science in Sport and Exercise. - : Springer Science and Business Media LLC. - 2662-1371 .- 2096-6709. ; 3, s. 281-291
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Tidskriftsartikel (refereegranskat)abstract
- PurposeTo biomechanically profile force generation connected to the complex role of the trunk in double poling in a representative sample of Para-Nordic sit-skiers.MethodsTwelve male World Cup Para-Nordic sit-skiers (sport classes: LW10–12) were skiing on flat snow terrain at submaximal speed of 4.5 m/s (~ 73% maximum speed). 2D video (50 Hz) and pole force analyses (1000 Hz) were performed synchronously, examining angle, force and cycle characteristics to analyse the role of the trunk in generating propulsion.ResultsLW10–11.5 skiers lost between 21% and 4% propulsive force versus LW12 athletes only due to different geometrics of the trunk and pole angle at an equal axial pole force. While LW10–11 skiers indicated trunk extension or position maintenance during pole thrust, LW11.5–12 skiers showed strong trunk flexion combined with smaller pole angles to the ground. Hence, LW11.5–12 skiers could create larger propulsive forces and therefore greater cycle lengths at lower cycle rates at the same speed. Maximum speed increased from LW10 to LW12 and was significantly correlated to trunk flexion range of motion (r = 0.63) and cycle length (r = 0.59). Trunk flexion ROM showed a significant relationship to the impulse of propulsive force (r = 0.63) and pole angle to the ground (r = − 0.76) (all P < 0.05).ConclusionThe impact of impairment on the force production profiles and its physiological-biomechanical consequences need further investigation also in other terrains and at wider spectrums of skiing speeds. The evident problem of low numbers of LW10–11 skiers in World Cup needs creative future solutions for research.
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| 2. |
- Salier Eriksson, Jane
(författare)
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The heart rate method for estimating oxygen uptake in walking and cycle commuting : Evaluations based on reproducibility and validity studies of the heart rate method and a portable metabolic system
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Walking and cycling to work can contribute to population health, but more objective knowledge concerning exercise intensities, oxygen uptake and the metabolic demands of this physical activity is needed for this and other evaluations. To attain this, valid and reliable instruments are a requirement. The focus of this thesis was to evaluate whether the heart rate method can be used for this purpose. It involves establishing the relation between heart rate and oxygen uptake during ergometer cycling in laboratory conditions, and thereafter checking if the same relation exists during cycle or walking commuting in a metropolitan area.To accomplish this, a portable metabolic system was tested for validity and reliability in laboratory and field conditions and the reproducibility of the heart rate and oxygen uptake relation in the laboratory was evaluated. Furthermore, the heart rate and oxygen uptake relations during cycle and walking commuting was compared with those attained in the laboratory.The first two studies showed that a portable metabolic system is valid during laboratory and sustained field conditions. Studies 3 and 4 showed that the heart rate method with respect to the heart rate-oxygen uptake relationship is reliable on the group level for both walking and cycling commuters during repeated measures in the laboratory. The last two studies showed that applying the heart rate method during cycle commuting leads to valid levels of oxygen uptake on the group level for both males and females. Contrary to that, the measured levels of oxygen uptake in the field during walking commuting were on average 17% higher for males, and 13% higher for females than the values obtained with the heart rate method. For both walking and cycling commuters, the individual spread around the mean values was rather high, creating somewhat wide confidence intervals for the mean values.In summary, the heart rate method can be used for cycle commuters during their normal commuting conditions, while for pedestrians it is necessary to take into account that oxygen uptake per heart rate is higher while walking than that estimated from ergometer cycling in the laboratory.
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| 3. |
- Andersson, Ulrika, et al.
(författare)
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Inactivation of aconitase and oxoglutarate dehydrogenase in skeletal muscle in vitro by superoxide anions and/or nitric oxide.
- 1998
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Ingår i: Biochemical and Biophysical Research Communications - BBRC. - : Elsevier BV. - 0006-291X .- 1090-2104. ; 249:2, s. 512-6
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Tidskriftsartikel (refereegranskat)abstract
- Strips of rat soleus muscle were incubated in media containing a superoxide generating system and/or the nitric oxide donor sodium nitroprusside (SNP) before the maximal catalytic activities of aconitase, citrate synthase, and oxoglutarate dehydrogenase were measured. The maximal activities of aconitase and oxoglutarate dehydrogenase were both decreased by 25-30% by superoxide anions; however, only the maximal activity of aconitase was decreased, by approximately 50%, by incubation of muscles with SNP. Furthermore, when both superoxide and NO were present in the medium, aconitase activity was decreased by 70%. The maximal activity of citrate synthase was not affected by any of the treatments. This is the first time that superoxide anions or NO has been shown to inactivate aconitase and oxoglutarate dehydrogenase in skeletal muscle. It is suggested that these effects may be responsible for some alterations in skeletal muscle metabolism, and these possibilities are discussed.
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| 6. |
- Arndt, Anton, 1968-, et al.
(författare)
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Non-uniform displacement within the Achilles tendon durig passive ankle joint motion.
- 2012
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Ingår i: Knee Surgery, Sports Traumatology, Arthroscopy. - : Springer Science and Business Media LLC. - 0942-2056 .- 1433-7347. ; 20:9, s. 1868-74
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE:An initial step in the understanding of Achilles tendon dynamics is to investigate the effects of passive motion, thereby minimising muscle activation and reducing internal joint forces. Internal tendon dynamics during passive ankle joint motion have direct implications for clinical rehabilitation protocols after Achilles tendon surgery. The aim of this study was to test the hypothesis that tendon tissue displacement is different in different layers of the Achilles tendon during controlled passive ankle joint movements.METHODS:Ultrasound imaging was conducted on the right Achilles tendon of nine healthy recreationally active males. Standardised isokinetic passive dorsi-plantar-flexion movements were performed with a total range of motion of 35°. The tendon was divided into superficial, central and deep layers in the resulting B-mode ultrasound images viewed in the sagittal plane. A block-matching speckle tracking algorithm was applied post-process, with kernels for the measurement of displacement placed in each of the layers.RESULTS:The mean (SD) displacement of the Achilles tendon during passive dorsiflexion was 8.4 (1.9) mm in the superficial layer, 9.4 (1.9) mm in the central portion and 10.4 (2.1) mm in the deep layer, respectively. In all cases, the movement of the deep layer of the tendon was greater than that of the superficial one (P < 0.01).CONCLUSIONS:These results, achieved in vivo with ultrasonographic speckle tracking, indicated complex dynamic differences in different layers of the Achilles tendon, which could have implications for the understanding of healing processes of tendon pathologies and also of normal tendon function.
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| 8. |
- Arvidsson, Daniel, 1974, et al.
(författare)
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Reexamination of Accelerometer Calibration with Energy Expenditure as Criterion: VO2net Instead of MET for Age-Equivalent Physical Activity Intensity
- 2019
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Ingår i: Sensors. - : MDPI AG. - 1424-8220. ; 19:15
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Tidskriftsartikel (refereegranskat)abstract
- Accelerometer calibration for physical activity (PA) intensity is commonly performed using Metabolic Equivalent of Task (MET) as criterion. However, MET is not an age-equivalent measure of PA intensity, which limits the use of MET-calibrated accelerometers for age-related PA investigations. We investigated calibration using VO2net (VO2gross - VO2stand; mL.min(-1).kg(-1)) as criterion compared to MET (VO2gross/VO2rest) and the effect on assessment of free-living PA in children, adolescents and adults. Oxygen consumption and hip/thigh accelerometer data were collected during rest, stand and treadmill walk and run. Equivalent speed (Speed(eq)) was used as indicator of the absolute speed (Speed(abs)) performed with the same effort in individuals of different body size/age. The results showed that VO2net was higher in younger age-groups for Speedabs, but was similar in the three age-groups for Speed(eq). MET was lower in younger age-groups for both Speed(abs) and Speed(eq). The same VO2net-values respective MET-values were applied to all age-groups to develop accelerometer PA intensity cut-points. Free-living moderate-and-vigorous PA was 216, 115, 74 and 71 min/d in children, adolescents, younger and older adults with VO2net-calibration, but 140, 83, 74 and 41 min/d with MET-calibration, respectively. In conclusion, VO2net calibration of accelerometers may provide age-equivalent measures of PA intensity/effort for more accurate age-related investigations of PA in epidemiological research.
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| 10. |
- Durrant, Christelle, et al.
(författare)
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Defects in Galactose Metabolism and Glycoconjugate Biosynthesis in a UDP-Glucose Pyrophosphorylase-Deficient Cell Line Are Reversed by Adding Galactose to the Growth Medium.
- 2020
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Ingår i: International Journal of Molecular Sciences. - : MDPI. - 1661-6596 .- 1422-0067. ; 21:6
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Tidskriftsartikel (refereegranskat)abstract
- UDP-glucose (UDP-Glc) is synthesized by UGP2-encoded UDP-Glc pyrophosphorylase (UGP) and is required for glycoconjugate biosynthesis and galactose metabolism because it is a uridyl donor for galactose-1-P (Gal1P) uridyltransferase. Chinese hamster lung fibroblasts harboring a hypomrphic UGP(G116D) variant display reduced UDP-Glc levels and cannot grow if galactose is the sole carbon source. Here, these cells were cultivated with glucose in either the absence or presence of galactose in order to investigate glycoconjugate biosynthesis and galactose metabolism. The UGP-deficient cells display < 5% control levels of UDP-Glc/UDP-Gal and > 100-fold reduction of [6-3H]galactose incorporation into UDP-[6-3H]galactose, as well as multiple deficits in glycoconjugate biosynthesis. Cultivation of these cells in the presence of galactose leads to partial restoration of UDP-Glc levels, galactose metabolism and glycoconjugate biosynthesis. The Vmax for recombinant human UGP(G116D) with Glc1P is 2000-fold less than that of the wild-type protein, and UGP(G116D) displayed a mildly elevated Km for Glc1P, but no activity of the mutant enzyme towards Gal1P was detectable. To conclude, although the mechanism behind UDP-Glc/Gal production in the UGP-deficient cells remains to be determined, the capacity of this cell line to change its glycosylation status as a function of extracellular galactose makes it a useful, reversible model with which to study different aspects of galactose metabolism and glycoconjugate biosynthesis.
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